1. Field of the Invention
The present invention is related to a polishing pad, and more particularly, to a polishing pad with two groove patterns.
2. Description of the Prior Art
Electrical chips are formed by deposition of various laminate materials, for example, a silicon wafer is one of the substrates of laminate materials. Whenever a new laminate is deposited, a polishing or scrapping step is often needed for removing excessive laminate materials to planarize the chip or to achieve other purposes. Such process of polishing is generally called chemical mechanical polishing (CMP). Since chips are formed by deposition of different thin film laminates, the CMP step needs to be performed for multiple times for evenly removing excessive laminate materials from the surface of a chip to achieve the purpose of planarization.
And usually when the CMP step is performed, chemical slurry is led in between the chip and the polishing pad for generating chemical reaction between the deposited thin film laminates and the chemical slurry or for generating mechanical reaction between the deposited thin film laminates and the particles in the chemical slurry to remove part of excessive thin film laminates on the surface of chip. However, the slurry existing between the polishing pad and the chip makes it easy for the polishing pad and the chip to become fully attached to each other, which thus causes disappearance of the force of friction between the polishing pad and the chip. Therefore, in order to achieve better polishing effect with the CMP step, the most common practice at present is to install groove on the surface of the polishing pad not only for increasing force of friction between the polishing pad and the chip but also for ensuring that the slurry is evenly distributed on the surface of the polishing pad and for letting polishing particles suspended in the slurry and the scraps to flow out through the groove.
In prior art, many patents make improvements particularly on the pattern of groove installed on the surface of polishing pad. Taking Taiwan patent No. I250572 for one example, referring to FIG. 1A, groove 11 is formed on the surface side of polishing pad 10, the pattern of which being selected from the group consisting of ring-shape, grid-shape, and helix-shape, FIG. 2A being a sectional view drawn according a-a′ sectional line in FIG. 1A; taking Taiwan patent No. 200744786 for another example, referring to FIG. 2, the polishing pad 20 includes two sets of grooves on its surface, one set being the first kind of grooves 21 that intersect a single virtual direct line extending from center of polishing pad 20 to surround, the set of groove 21 does not intersect each other, the other set being the second kind of grooves 22 that extend from central part of polishing surface to the surrounding part, are composed of the second kind of grooves 22 contacting each other at the central part and the second kind of grooves 22 does not contact any other second kind of grooves 22 at the central part, and do not intersect each other.
Although the main objective of the aforementioned patents is to effectively eliminate scratches caused by impurities produced in the interior when the polishing step is performed, yet when the scraps produced after polishing or the polishing particles in the slurry are larger than the groove, they cannot instantly flow out via the groove of polishing pad. And thus the residual polishing particles or deposits will form larger particles and easily cause scratching and damaging of surface of the polished work piece.